The technology of connecting two or more construction elements using impact-driven helically profiled fasteners, that is to say helical fixings having loosely wound thread-forming blades, has been commercially practised for the past 20 years. The helical fasteners rely upon the peaks and troughs of a deep set helical profile to interlock within the host material to provide anchorage.
In their simplest form the fasteners are used as headless and flush finish screw-nails that are simply hammered into nailable layers whereupon they cut a helical interlocking path of penetration. One of the more common applications is in the connection or reconnection of two or more masonry units, whereby long slender versions of the fastener are utilised to tie two layers of a cavity structure.
Hammer drill attachments and telescopic driving mechanisms have been fabricated to increase insertion rates for helical fasteners, which are impactingly driven and recessed into pilot holes that have been pre-drilled into masonry walls.
One specific example of a power driven fastening mechanism is revealed in U.S. Pat. No. 5,586,605, which demonstrates and claims a complex helical tie-driving tool having a combination of parts that have means to circumferentially contain the full diameter of a helical tie and telescopic workings to recess it into a pilot bore such as to deliver a continuous driving and recessing wall tying technique.
Such telescopic mechanisms are, by nature, highly elaborate and such intricacy has detrimental consequence in terms of operational reliability and cost. Indeed insertion tools of this type, or of similar design and function, commonly sell for around one hundred and seventy five US dollars. On the assumption that such a tool has a reliable life or is useful for say 2000 fixing installations, the tooling costs equate to a hefty nine US cents per fastener. However in instances where the user only has a few hundred fasteners to fix, for example where a user has to fix only 200 fasteners, yet still has to spend one hundred and seventy five US dollars for an installation tool, the tooling cost equates to a prohibitive ninety US cents per fixing. Such tooling expenditure is commercially flawed, in terms of cost off-set, and as such is an impediment to the saleability and wide spread exploitation of well established fasteners.
Furthermore such telescopic driving tools rely upon an impacting confrontation with a hosting layer to force a telescoping reaction by which to recess the tie. Such pounding confrontation provides further cost penalty prospect in terms of damage repair to a hosting layer; for example for the repair of damage to a buildings' façade.
A further disadvantage of telescopic driving apparatus is the length of the assembled installation arrangement in use, which in concentric combination comprises the fastener, the extended telescopic insertion tool and the powered machinery that energises the tool. Such lengthy assemblies are operationally cumbersome and may compromise the usability of such a system, particularly in confined spaces. The arrangement of an average 9 inch (230 mm) long wall tie fitted in a telescopic insertion adapter that is in turn fitted to a small rotary hammer drill is over 32 inches (800 mm) long and weighs between 7-9 lb (3-4 kg). The process of offering up and concentrically aligning the entire set up to an average ¼ inch (6.35 mm) pilot hole is itself cumbersome. The further unwieldy process of operating the rotary hammer drill in one hand and using the other outstretched hand to restrain the hefty set up axially and rotationally during the driving operation serves to compound handling difficulties and operator fatigue.
Issues of health and safety can exist with power driven fixings. It will be appreciated that this type of telescopic tool usually operates under a high speed rotary hammer action and is invariably used far above the ground. A complex mechanism in this form can have very severe consequences if it jams or ‘snatches’ due to malfunction, loss of lubrication or breakage.
Thus there is a need to provide a more manageable, reliable and cost effective means and method of tying components with helically profiled fasteners.
Accordingly, the invention seeks to mitigate at least one of the above-mentioned problems or provide an alternative means for and method of inserting helically profiled fasteners into a structure.